According to a Japanese article, “between the single-player adventure and all of its hidden side-quests, there are over 100 hours of gameplay to be experienced. Also on the subject of size, it’s said that the game in general is much bigger than any Zelda before it. Finally, the article goes on to relay that the fresh and new gameplay mechanics introduced in Twilight Princess will set the benchmark for the next generation of Zelda” (emphasis mine).
If you remember, the last time we heard an indication of length, Aonuma guesstimated 70 hours. Whether his estimate was strictly storyline or included side-quest tallies as well, I can’t say for certain, but I think something interesting to point out is that, out of all the RPGs I have ever heard of (the only games that are typically measured in “hours”), I have never heard of any non-MMORPG lasting 100+ hours. (You all can correct me if I’m wrong, but even Final Fantasy X didn’t advertise that, and it was a huge game. Perhaps I’m trying to count my cuccos before their hatched, but I believe that this not only sets a benchmark for Zelda, it will set a benchmark for all RPGs to come.